Originally Posted by deerebowtie
what is the wheel base? why put the brownie boxes behind the tcase?
Originally Posted by kargod
Couldn't the gearing of one overdrive unit be adjusted to eliminate the mechanical advantage of having two units?
I'm just trying to see why you feel you need two units?
That, and as asked, why you wanted them post transfer case?
I am using the 2 3 speed(2.0,1.0,.72)brownies to get a .72 and .51 ratio. They will also let me split the gears depending on the load.
I was going to use one (2.0,1.3, 1.0 box) and run a .5/1 gear reduction before it. The fact is the Under, under, direct box is a lot harder to find and would be harder to get parts for if I needed to replace it. The cost of a .5/1 box is more then a second brownie and if broke I would be screwed.
Finding the more popular under direct over (2.0, 1.0, .72)brownie is a lot easier. These boxes are more similar to 2 speed rear end then a transmission having 2 pinion yokes. Changing gears is complicated and not worth the hassle. I am going the simpler route that I know will work.
This is for a tow rig I do not need the low ratio before the transfer case. The truck has a 65/1 craw now. That is enough for something where the 4wd will only be used in light muddy conditions. I don't actually need the low ratio at all it is just easier to find the boxes with the under,direct, over.
Originally Posted by boggin-machine
he over thinks shit and isnt actually going to do it. this doesnt make any sense to do this at all. what are you trying to actually build?
I am doing it and it does make sense. It gives me a very reliable .72 and .52 overdrive while letting me keep the low gearing in the rear end for towing. Mounting 2 brownies is the toughest, easiest to replace, and most simplistic drive train that will give me the ratios I want without replacing the entire power train.
I have done the math a few hundred times. It will pull 13k(conservative number) up a 6% grade maintaining 55 mph easily. I know that is not impressive by today's standards. But, it is better then most and will work for this rig. The impressive numbers are below 52 mph where most of the work is done.
The .52 ratio is only used above 55 to reduce wear. I plan on maintaining a towing speed between 55 and 65 in this. I don't see myself driving faster then 70 empty to save both wear and fuel. I can drive 70 without using the second overdrive If need be. But the engine is out of the power range going that speed increasing wear and reducing mileage. Using the second overdrive keeps the engine in the power range from 52-72 mph.
I am simply seeking advise if I can eliminate the center yokes in a effort to lengthen the rear drive shaft. I do have the wheel base to make this work either way. If I can eliminate the center yokes it means less parts to replace and the less chance of vibration.
With everything in line I believe eliminating the center yokes is possible. Maybe I am missing something though. Which is why I am looking for feedback from people that have more experience in(old school) dual divorced transfer case setups and such.